Differences between rats and undernourished preweaning, and controls in learning about a redundant stimulus during acquisition of a conditioned emotional response.
Male rats were undernourished during the first three weeks of life by restricting maternal food consumption. Following nutritional rehabilitation, previously undernourished (PU) and control (C) rats were trained to operate a lever to obtain food reward on a variable interval schedule. When rates of responding had stabilised, the rats were tested for suppression of lever-pressing during the illumination of a light which preceded footshock. There were not differences between PU and C groups in the acquisition of this conditioned emotional response, nor were there differences in suppression when a redundant, tone stimulus was presented contemporaneously with the light to predict shock. When the tone was subsequently tested alone for its ability to suppress lever-pressing it was found to have acquired this property in C, but not in PU animals. In a second experiment, PU and C rats were found not to differ in their response to the tone when it was presented as a novel stimulus, nor in suppression to the tone when it was made the sole predictor of footshock. It was concluded that PU and C rats differed in learning about a stimulus predicting footshock, only when that stimulus was redundant. Among the possible explanations for this behavioural difference between PU and control rats are differences in motivation, curiosity, or strength of conditioning. These possibilities are evaluated within the context of current formal theories of conditioning.
D000818:Animals; D000831:Animals, Newborn; D001245:Association Learning; D003216:Conditioning, Operant; D004193:Discrimination Learning; D004597:Electroshock; D004644:Emotions; D005260:Female; D008297:Male; D009115:Muridae; D011247:Pregnancy; D011502:Protein-Energy Malnutrition / Q000523:psychology*